1. Field of the Invention
This invention relates to a tree trimming apparatus which is especially suitable for the airborne trimming of rights-of-way adjacent to electric power lines at a selected distance from the ground. More particularly, the invention relates to a trapeze mount for suspending an airborne tree trimming apparatus during functional cutting configuration and facilitates pivoting of the tree trimming apparatus into horizontal, stored location on ground supports when not in use. In a preferred embodiment, the tree trimming apparatus includes an articulated boom designed for suspension beneath a helicopter undercarriage by means of a trapeze mount, with ten or more rotating circular blades mounted in coplanar, closely-spaced, tandem relationship on the boom. The circular saw blades are typically powered by an internal combustion engine mounted on a drive or engine assembly of the boom and extend outwardly of the boom structure to facilitate cutting large tree branches which are six to eight inches or more in diameter, as well as smaller woody growth.
The trapeze and boom-mounted circular saw blades rotate in a substantially vertical plane when operational, with all blades oriented outwardly of the supporting boom. The trapeze mount is designed to facilitate rearward extension of the boom and the circular saw blades when the boom and circular saw blades are lowered on supports mounted on the ground and downward extension of the boom and saw blades in functional, cutting configuration when the helicopter is airborne. Accordingly, as the helicopter passes along the edge of a row of trees to be cut, the circular saw blades are always oriented on the tree-side of the boom and are adapted to engage and cut the branches through. The severed branches then fall away on the boom-side of the tree trimming apparatus. The boom carrying the saw blades is connected to a boom mount bar in the trapeze mount, by means of a lower pivot collar which allows the boom and saw blades to swing laterally from side to side with respect to the flight path of the helicopter. The boom is also pivotally-mounted with the boom mount bar about a transverse axis which is substantially perpendicular to the direction of motion of the helicopter, a feature which not only aids in properly orienting the apparatus during take-off and landing, but also permits the apparatus to yield slightly to the rear when encountering numerous or large branches during airborne operation. Thus, while the helicopter speed may be five to ten feet per second, the forward cutting speed of the circular saw blades through very large branches along the flight path beneath the helicopter may be somewhat less than this speed. The greater the average speed which is attainable for the helicopter at effective cutting rates, the more cost-effective the clearing operation will be.
The problem of encroachment of trees and other woody growth in power line rights-of-way and other locations which need to be kept free of trees and brush has been commonly solved with ground or air-applied herbicides. Helicopters have long played a large and important role in spraying herbicides to prevent the encroachment of trees and plants on such rights-of-way. However, the spraying of herbicides for woody growth control is sometimes undesirable, particularly during windy weather, since the herbicide is sometimes blown from the rights-of-way onto adjacent crops and animals. The alternative of cutting encroaching tree branches and other woody growth using ground vehicles or on foot has proved to be very expensive and time consuming, particularly in remote areas.
2. Description of the Prior Art
The use of multiple, air-borne, hydraulically-operated circular saw blades mounted on a boom for use in trimming trees along power line rights-of-way is detailed in U.S. Pat. No. 4,544,781, dated Nov. 26, 1985, to Randall Rogers. A "Ground-Operated Apparatus for Trimming Trees, Orchards and Like Applications" is detailed in U.S. Pat. No. 4,067,178, dated Jan. 10, 1978, to Charles Miller. While perhaps suitable for use in the orderly environment of a fruit orchard, such ground vehicle-mounted equipment is of limited use in trimming trees adjacent to electric utility rights-of-way in rural and remote areas. Furthermore, apparatus such as that detailed in U.S. Pat. No. 4,067,178, is clearly not adaptable for mounting on a helicopter or other aircraft. A number of other patents disclose multiple circular saw blades for tree trimming purposes, the most pertinent of which patents are listed below. These patents describe non-coplanar, circular saw blades which are used in controlled, ground vehicle-supported tree trimming apparatus:
______________________________________ U.S. Pat. No. Patentee: Date Issued: ______________________________________ 3,487,615 C. O. Leydig, et April 1, 1968 3,913,304 Paul Jodoin October 21, 1975 3,952,485 L. R. McRobert April 27, 1976 4,302,922 H. F. Guerndt, Jr. et al December 1, 1981 ______________________________________
My co-pending U.S. patent application Ser. No. 07/197,025, filed May 20, 1988, entitled AirBorne Tree Trimming Apparatus, details an airborne tree trimming apparatus for installation on a helicopter, which apparatus includes a boom extension vertically suspended from the helicopter and multiple circular saw blades arranged in tandem, coplanar relationship on an operating boom which is attached to the boom extension by means of a boom pivot. Circular saw blades are designed to rotate about parallel, substantially horizontal axes which are oriented substantially at right angles to the normal direction of motion of the helicopter and are belt-driven by an internal combustion engine that is also mounted on the operating boom above the circular saw blades. The boom is attached to a quick-release hook which engages the top of the boom structure to facilitate towing of the boom and the saw blades beneath the helicopter in cutting configuration and resting the boom and saw blades on spaced, ground-oriented supports after the cutting operation is complete.
The present invention permits rapid and accurate trimming of trees adjacent to electric utility and other rights-of-way in a safe and efficient manner by suspending an airborne tree trimming apparatus from a helicopter or like aircraft, using a trapeze mount to facilitate more accurate cutting and easier deployment of the saw blades and boom into and out of the cutting configuration. In use, the articulated tree trimming apparatus is suspended from the trapeze mount such that the circular saw blades slope slightly rearwardly from the attachment point at the trapeze along a flight path beneath the helicopter, and such that very small branches and woody growth cannot pass between any two adjacent blades without being cut. A primary factor in the cutting efficiency of the circular saw blades is the mounting of the blades and boom in a substantial, stable, yet pivoting or folding manner, to permit the large and heavy blades to cut through limbs of substantial size while the apparatus is airborne. Take-off and landing with the trapeze-equipped apparatus is a simple matter for a qualified helicopter pilot, due to the design of the trapeze and the front-to-rear articulation of the operating boom with respect to the boom extension, which permits the apparatus to be oriented on a pair of spaced, ground-supporting cradle supports beneath the helicopter at take-off or landing.
In addition to providing the above described features and advantages, it is an object of this invention to provide a helicopter-mounted trapeze mount for an airborne tree trimming apparatus, wherein the tree trimming apparatus is suspended from the trapeze mount and includes a downward-extending, articulated boom carrying a plurality of adjacent, powered circular saw blades, to provide a cutting path or swath in woody growth along a predetermined flight path.
It is another object of the invention to provide a trapeze mount pivotally attached to a helicopter and adapted to receive and support a boom equipped with multiple internal combustion engine-driven circular saw blades mounted in tandem, substantially co-planar relationship on the boom. The boom is mounted to the trapeze by means of a boom mount bar and sliding collar, in order to facilitate selectively carrying the boom in downwardly-suspended cutting configuration and resting the boom on supports located on the ground as the boom is disposed beneath and rearwardly of the helicopter pursuant to pivoting of the trapeze mount.
Still another object of the invention is to provide a self-contained, helicopter-mounted trapeze apparatus and an airborne tree trimming device pivotally suspended from the trapeze apparatus by means of a boom mount bar and sliding collar, which tree trimming device is capable of being powered independently of the helicopter by means of multiple circular saw blades arranged in tandem configuration on a substantially vertical operating boom and driven by a governer-controlled internal combustion engine, the circular saw blades being sufficiently large and heavy to generate significant momentum and inertia for optimum airborne cutting efficiency.
Still another object of the invention is to provide a trapeze apparatus for suspending a boom containing a set of spaced circular saw blades, wherein the trapeze is pivotally suspended from a helicopter and includes a boom mount bar having one end pivotally and releasably attached to a quick-release hook mounted on the helicopter and the opposite end stabilized on the trapeze by means of a sliding collar and attached to one end of a boom carrying rotating cutter blades, such that the trapeze can be deployed rearwardly of the helicopter along with the boom, to locate the boom and the cutting blades on the ground and the trapeze can be alternatively deployed downwardly from the airborne helicopter to suspend the boom beneath the helicopter in cutting configuration.